The present invention relates to a communication element, which a boundary scan element for use in a wiring check for an electronic circuit substrate is applied to, and a communication apparatus using the same.
A boundary scan test method is proposed as a method of checking whether or not ICs packaged in an electronic circuit substrate are properly interconnected or whether or not an internal processing is properly executed in the ICs themselves.
This boundary scan test method is the test method which is applied to the electronic circuit substrate comprising the ICs in which a boundary scan element is previously incorporated. This boundary scan test method has a feature that connection check or IC operation test for an circuit substrate having such a high density that a so-called in-circuit test method cannot be employed can be performed.
An example of the conventional boundary scan element is now outlined.
FIG. 3 is a block diagram of a logic IC 100 to be tested comprising the boundary scan element.
The IC 100 comprises input terminals 101, output terminals 102 and an internal logic 111, as a basic constitution. The IC 100 further comprises the boundary scan element. The boundary scan element comprises input-side boundary cells 103, output-side boundary cells 104, a TDI terminal 105 to which data is inputted, a TDO terminal 106 from which the data is outputted, a TMS terminal 107 to which a signal for switching operation modes is inputted, a TCK terminal 108 to which a clock signal is inputted, a TRS terminal 109 to which a reset signal is inputted and a TAP circuit 110.
The input-side and output-side boundary cells 103 and 104 are separately provided for the respective input and output terminals 101 and 102. All the boundary cells 103 and 104 are connected in series in chain together.
The TDI terminal 105 and the TDO terminal 106 are connected to the input-side boundary cell 103 and the output-side boundary cell 104, respectively, of the boundary cells 103 and 104 located at both the ends.
While the TAP circuit 110 is synchronized to the clock signal from the TCK terminal 108, the TAP circuit 110 executes the processing in accordance with the signal for switching the operation modes from the TMS terminal 107. That is, the data is shifted to the boundary cells 103 and 104, or the data is inputted and outputted between the boundary cells 103 and 104 and the internal logic 111 or the input or output terminals 101 or 102. The TAP circuit 110 enters a reset state in accordance with the reset signal from the TRS terminal 109. This TRS terminal 109 is not always needed because the reset state can be included in one of commands to switch the operation modes from the TMS terminal 107.
In the method of testing the IC 100 comprising such a constitution, the operation test for the IC is performed, e.g., as follows: test data is inputted from a host computer to the TDI terminal 105 in a serial form, and the test data is shifted and set to each of the input-side boundary cells 103. Then, the set test data is outputted to and processed by the internal logic 111. Subsequently, the data from the internal logic 111 is set to the output-side boundary cells 104, and this data is then returned from the TDO terminal 106 to the host computer in the serial form. The host computer compares the returned data with the test data which the host computer previously sent out, whereby the host computer can distinguish whether or not the internal logic 111 normally operates.
The test for the connection between the ICs is carried out, e.g., as follows: the test data is sent and set from the host computer to the output-side boundary cells 104 through the TDI terminal 105 and the input-side boundary cells 103. This data is sent out from the output terminals 102 to another IC connected to the output terminals 102 of the IC 100.
Then, the host computer compares the test data which another IC received with the test data which the host computer had previously sent out, whereby the host computer can distinguish whether the wiring between the ICs is connected or disconnected, or the like.
On the other hand, the inventor has focused on the usefulness of the boundary scan element not as the element only for checking the wiring connection or the like but as a communication element for controlling various terminal equipment such as a CCD camera. The inventor has therefore proposed a communication apparatus in which this boundary scan element is applied to the communication element (International Publication No. WO98/55925).
However, the conventional boundary scan element is not satisfactory in a data transfer rate as the communication element.
That is, the conventional boundary scan element has a problem as follows: in order to set the data inputted from the TDI terminal 105 to each of the boundary cells 103 or 104, the data in each of the individual boundary cells 103 or 104 must be shifted sequentially.
This problem is similarly caused when the data set in the boundary cells 103 or 104 is outputted from the TDO terminal 106. The data transfer rate is not sufficient, particularly in the case of a large number of boundary cells 103 and 104.
It is therefore an object of the present invention to provide a communication element, which the boundary scan element is applied to and which can increase the data transfer rate, and a communication apparatus using the same.
According to the present invention, there is provided a communication element which comprises a plurality of input-side boundary cells; a plurality of output-side boundary cells corresponding to the input-side boundary cells; and a TAP circuit for controlling the input and output of data to/from the input-side and output-side boundary cells, the TAP circuit being connected to a TCK line to which a clock signal is inputted, a TMS line to which a mode signal for switching operation modes is inputted, and data input and output lines for inputting and outputting the data to/from terminal equipment which is an object of communication, wherein the input-side boundary cells are connected in parallel to the corresponding output-side boundary cells through the TAP circuit.
In this element, the boundary cells are not connected in series in chain together like the prior art, but the input-side boundary cells are connected in parallel to the corresponding output-side boundary cells through the TAP circuit.
Thus, the data stored in the input-side boundary cells can be transferred to the corresponding output-side boundary cells by one processing. Consequently, a data transfer rate can be increased.
In the communication element of the present invention, the boundary cells are not connected in series. To input or output the data between the communication element and the host computer or the like, the data is thus inputted or outputted directly to/from the boundary cells in a parallel form, not in a serial form through a TDI or TDO terminal like the prior art.
According to the present invention, there is provided a communication apparatus, which comprises a plurality of communication elements of the present invention; terminal equipment separately connected to each of the communication elements, for inputting and outputting the data to/from the communication elements through the data input and output lines; and a host computer, wherein the communication elements are connected in series manner to the host computer.
According to this means, the use of the communication element of the present invention allows increasing the data transfer rate at which the data is transferred between the communication elements and between the communication element and the host computer. Thus, the large amount of data can be processed. In the present invention, the terminal equipment means the object which the communication apparatus of the present invention communicates with. For example, a monitoring apparatus installed in every floor or room of a building, a security apparatus or various robots in a production line correspond to this terminal equipment. Since the communication apparatus of the present invention can transfer the data at high rate, the terminal equipment requiring the large-capacity data, in particular, can be also the object of communication.